Experts have been concerned about an uptick in cases of the uncommon disease, which typically strikes young children and results in muscle weakness and possible paralysis, respiratory failure and even death. The CDC has so far confirmed 134 cases in 33 states — but the agency announced Monday that it expects the number of possible AFM cases to decline for the rest of 2018.

While 18 new cases have been confirmed since last week, the CDC says the rate of reported cases has slowed, and that most people recently diagnosed with AFM became sick in September or October, suggesting that fewer new illnesses are emerging. A total of 299 possible cases had been referred to the CDC this year, as of Nov. 30.

While there’s still a lot experts don’t know about AFM — including, most importantly, what causes it and how best to treat it — health officials have noted distinct seasonal patterns associated with the condition. Its case count has spiked every-other year since an outbreak in 2014, and in each of those years, the majority of cases were reported from August through October, before slowing significantly in November. This year’s outbreak appears to be in keeping with those trends.

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The CDC last month assembled a task force of medical and public health officials to better understand the mysterious condition. That group may be especially crucial, given recent research findings around AFM.

In November, a small retrospective study found that what looked to be a promising treatment for AFM did not, in fact, significantly improve disease outcomes. And last week, a small paper published in JAMA Pediatrics found that about a fourth of 45 children who met the CDC’s criteria for AFM between 2012 and 2016 had alternate neurologic conditions, pointing to the difficulty of accurately diagnosing and assessing AFM.